feat(backend/story-integration): Phase 5 - Audio Generation

- Fixed audio file path generation in StoryGenerationService.GenerateAudioAsync
- Audio files now stored at wwwroot/audio/story/level{id}-segment{order}.wav
- Added static file serving in Program.cs (app.UseStaticFiles)
- Added wwwroot/audio/story directory creation on startup
- Updated StoryController.GetSegmentAudioAsync to return audio URL
- Static file middleware serves audio files automatically
- All 324 tests still pass

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

GermanApp/Application/Services/StoryGenerationService.cs

@@ -227,25 +227,31 @@ public class StoryGenerationService
             return StorySegmentDto.FromEntity(segment);
         }
 
-        // Generate audio file path
-        var audioPath = $"/audio/story/level{segment.LevelId}-segment{segment.Order}.wav";
+        // Generate file system path for audio file (relative to current directory)
+        var audioDirectory = Path.Combine("wwwroot", "audio", "story");
+        var filename = $"level{segment.LevelId}-segment{segment.Order}.wav";
+        var audioFilePath = Path.Combine(audioDirectory, filename);
         
         try
         {
-            // Generate audio using the TTS service directly
+            // Ensure directory exists
+            Directory.CreateDirectory(audioDirectory);
+            
+            // Generate audio using the TTS service
             await _ttsService.GenerateAudioToFileAsync(
                 segment.Content,
-                audioPath,
+                audioFilePath,
                 null,
                 "de",
                 cancellationToken);
 
-            // Update segment with audio URL
-            segment.UpdateAudioUrl(audioPath);
+            // Convert to URL path for storage
+            var audioUrl = $"/audio/story/{filename}";
+            segment.UpdateAudioUrl(audioUrl);
             await _storyRepository.UpdateAsync(segment, cancellationToken);
 
-            _logger.LogInformation("Generated audio for segment {SegmentId}: {AudioPath}",
-                segmentId, audioPath);
+            _logger.LogInformation("Generated audio for segment {SegmentId}: {AudioUrl}",
+                segmentId, audioUrl);
 
             return StorySegmentDto.FromEntity(segment);
         }

GermanApp/Presentation/Controllers/StoryController.cs

@@ -411,8 +411,9 @@ public class StoryController : ControllerBase
             return NotFound();
         }
 
-        // In a real implementation, return the actual file
-        // For now, return the URL
+        // Static files are served from wwwroot, and audio files are stored at wwwroot/audio/story/
+        // The segment.AudioUrl is already in the format "/audio/story/levelN-segmentM.wav"
+        // The static file middleware will serve it automatically
         return Ok(new { AudioUrl = segment.AudioUrl });
     }
 

GermanApp/Program.cs

@@ -22,6 +22,7 @@ using Microsoft.Extensions.Caching.Memory;
 using Microsoft.Extensions.Options;
 using Microsoft.IdentityModel.Tokens;
 using Serilog;
+using System.IO;
 using System.Text;
 
 // Configure Serilog
@@ -218,11 +219,17 @@ try
 
     var app = builder.Build();
 
+    // Create static file directories
+    Directory.CreateDirectory(Path.Combine("wwwroot", "audio", "story"));
+
     // Configure the HTTP request pipeline.
     
     // Use exception middleware first (to catch all exceptions)
     app.UseExceptionMiddleware();
 
+    // Serve static files (audio, etc.)
+    app.UseStaticFiles();
+
     if (app.Environment.IsDevelopment())
     {
         app.MapOpenApi();

docs/features/story-integration.md

@@ -1,7 +1,7 @@
 # Feature: Story Integration
 
 > **Status**: 🚀 In Progress  
-> **📊 Current Progress**: Phase 1-4 ✅ Complete (Database & Models, Backend Services, Unit Tests, AI Integration), Phase 5 Next (Audio Generation)
+> **📊 Current Progress**: Phase 1-5 ✅ Complete (Database & Models, Backend Services, Unit Tests, AI Integration, Audio Generation), Phase 6 Next (Frontend Integration)
 > **Priority**: High  
 > **Complexity**: High  
 > **Estimate**: 8-12 hours  
@@ -165,12 +165,12 @@ Order: 1
 - [x] Handle AI API errors gracefully (AiServiceException with error codes)
 - [x] Add retry logic for failed generations (ExecuteWithRetryAsync with exponential backoff)
 
-### Phase 5: Audio Generation (2 hours)
-- [ ] Integrate with Coqui TTS service
-- [ ] Generate audio for each story segment
-- [ ] Store audio files with consistent naming
-- [ ] Update StorySegment.AudioUrl after generation
-- [ ] Add audio file serving endpoint
+### Phase 5: Audio Generation (2 hours) - COMPLETE
+- [x] Integrate with Coqui TTS service (ITtsService, TtsService with CoquiConfig)
+- [x] Generate audio for each story segment (GenerateAudioAsync in StoryGenerationService)
+- [x] Store audio files with consistent naming (wwwroot/audio/story/level{id}-segment{order}.wav)
+- [x] Update StorySegment.AudioUrl after generation (segment.UpdateAudioUrl)
+- [x] Add audio file serving endpoint (UseStaticFiles + GET segments/{id}/audio)
 
 ### Phase 5: Frontend Integration (2-3 hours)
 - [ ] Create StoryPage component
@@ -194,7 +194,7 @@ Order: 1
 | Backend Services | June 13, 2025 | ✅ |
 | Unit Tests | June 13, 2025 | ✅ |
 | AI Integration | June 13, 2025 | ✅ |
-| Audio Generation | - | ⏳ |
+| Audio Generation | June 13, 2025 | ✅ |
 | Frontend Integration | - | ⏳ |
 | User Progress | - | ⏳ |
 
@@ -417,6 +417,7 @@ Make the story engaging and suitable for adult learners.
 | June 13, 2025 | Phase 1-2 Complete | Database & Models, Backend Services implemented |
 | June 13, 2025 | Phase 3 Complete | All unit tests written and passing (324 tests) |
 | June 13, 2025 | Phase 4 Complete | Enhanced prompts with CEFR-level-specific requirements for story generation |
+| June 13, 2025 | Phase 5 Complete | Audio generation with Coqui TTS, static file serving, and endpoints |
 
 ---